Who are you eternally? What do you represent in the eternal scale of time?

All living entities, regardless of what body they inhabit, are eternal servants of Krishna. In the eternal scale of time we represent an atomic spark of God’s consciousness. We represent Krishna’s marginal energy.

That the soul is marginal means it can be ruled either by Krishna’s internal potency, His spiritual potency, or it can ruled by His external potency - material nature. We are the same as God in quality, but different from Him in quantity.

Chaitanya Mahaprabhu says:

"It is the living entity's constitutional position to be an eternal servant of Krishna because he is the marginal energy of Krishna and a manifestation simultaneously one with and different from the Lord, like a molecular particle of sunshine or fire. Krishna has three varieties of energy.” —Madhya 20.109

Srila Prabhupada explains:

Srila Bhaktivinoda Thakura explains these verses as follows: Sri Sanatana Gosvami asked Sri Chaitanya Mahaprabhu, "Who am I?" In answer, the Lord replied, "You are a pure living entity.

You are neither the gross material body nor the subtle body composed of mind and intelligence. Actually you are a spirit soul, eternally part and parcel of the Supreme Soul, Krishna. Therefore you are His eternal servant. You belong to Krishna’s marginal potency.

There are two worlds -- the spiritual world and the material world -- and you are situated between the material and spiritual potencies. You have a relationship with both the material and the spiritual world; therefore you are called the marginal potency.

You are related with Krishna as one and simultaneously different. Because you are spirit soul, you are one in quality with the Supreme Personality of Godhead, but because you are a very minute particle of spirit soul, you are different from the Supreme Soul.

Therefore your position is simultaneously one with and different from the Supreme Soul. The examples given are those of the sun itself and the small particles of sunshine and of a blazing fire and the small particles of fire." Another explanation of these verses can be found in Adi-lila, Chapter Two, verse 96.